This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This pilot study will be a randomized, double-blind, placebo controlled, cross-over trial, designed to explore the effects of magnesium supplementation on insulin sensitivity, short-term consequences of improved insulin sensitivity, and on serum androgen levels in women with polycystic ovary syndrome.